EOS · CVE-2026-121368 · Infrastructure
FIX → 4.37.0F +4 ✓ verified
On Arista EOS devices configured with Bidirectional Forwarding Detection using keyed MD5 or keyed SHA1 authentication, a specially crafted BFD packet causes the system to reboot. An unauthenticated attacker with network adjacency to a BFD-enabled interface can trigger the reboot repeatedly to take the device offline.
first public Nov 10, 2026 · 2 sources
Could this affect your app?
Free first check from your website. Connect your repo for the full answer.
Arista EOS devices (switches, CloudEOS, cEOS-lab, vEOS-lab, CloudVision eXchange) running BFD with keyed MD5 or keyed SHA1 authentication (also meticulous mode). An unauthenticated attacker with direct or multi-hop network reachability to a BFD-enabled interface can send one crafted packet and reboot the device. Skip if BFD is unused or has no MD5/SHA1 authentication, or you run MOS, NetVisor, CloudVision Portal, CCF, DMF or VeloCloud, which Arista lists as not affected.
Not affected if bfd-not-configured, network-isolated, no-bfd-md5-sha1-auth, no-keyed-md5-or-sha1
Who cares arista-eos, bfd, network-devices, self-hosted
show running-config section router bfd and show running-config section bfd (per-interface config overrides global)authentication mode md5|sha1 shared-secret profile <name> (optionally ) is configured with live BFD sessions. shows On affected platforms running Arista EOS with Bidirectional Forwarding Detection (BFD) configured to use keyed MD5 or keyed SHA1 authentication, an unauthenticated attacker with network adjacency (direct or multi-hop) to a BFD-enabled interface can send a specially crafted BFD packet resulting in a system reboot.
This page as .md · .json · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
NVD data is provided by NIST and is public domain. Posts quoted belong to their authors.
Check it with your coding agent
It reads this page and tells you if your code is affected.
Are you affected?
Ask from here. InfraStack checks the affected versions against your stack and answers in your inbox.
InfraStack checks the affected versions against your stack and answers in Slack, with the evidence and the fix.
meticulousshow bfd peers detailAuthentication mode: Keyed Sha1/Keyed Md5/Meticulous Sha1/Meticulous Md5show version to affected releasesdebug rbfd 2 is setUpgrade to 4.37.0F +4